The effects of the longitudinal and transverse error of grating in the optical pick-up head of VCD, DVD,and CDROM during manufacturing on the transmittance and the ratio of intensity between the assistant and reading beam are analysed numerically by using the general expression of diffraction efficiency obtained from the scalar diffraction theory. The result shows that the longitudinal and transverse errors are compensable according to the assistant and reading beam, however, at the expense of transmittance loss. For grating in the optical pick-up head,the compensability between the longitudinal and transverse error practical references on the manufacture of grating.